1) Field of the Invention
This invention contains a method and device for using ultra high pressure waterdets contained within a vacuum shroud to remove coatings and other materials from deck tiedowns (see definition below). The device would be used on all interior and exterior decks of marine vessels (ships) containing tiedowns. Deck tiedowns are units permanently attached and incorporated into the deck either raised or recessed below the deck and are used to firmly attach items to the deck by means of chains, straps, binders, etc. Tiedowns are also known as padeyes, cloverleaves, D-rings, etc and come in several different designs. The typical parts of a tiedown as shown in FIGS. 1 and 1-A are the crossbars which are used to tie equipment down and the recessed cup which is either recessed below the surrounding deck surfaces 2 or elevated above the surrounding deck areas. These tiedowns are typically spaced 6-8 feet apart on the deck surface and typically cover the entire deck area on cargo decks, flight decks, hanger decks, weather decks, interior decks, trailer decks, etc of marine vessels.
2) Description of Prior Art
The cleaning of tiedowns for recoating purposes is usually accomplished as part of the deck maintenance program. The marine environment is extremely demanding on coatings and salt water is routinely trapped in the recessed areas of these tiedowns. The mechanical attachment of equipment to these tiedowns also damages coatings and leaves them susceptible to corrosion. Because the underside areas of the tiedowns are difficult to access they have historically not received proper surface preparation prior to recoating and preservation.
This poor surface preparation can cause repetitive cleaning and recoating which increases the cost of deck maintenance. Corrosion in these areas can cause premature deck failures and the loss of flight deck certification. Cleaning methods utilizing solid abrasives have been suspected of leaving foreign matter on decks which may cause engine damage to aircraft and other machinery located on the deck. This Foreign Object Damage (FOD) has caused the loss of many aircraft both fixed wing and helicopters.
Currently there are three existing methods of cleaning tiedowns during deck maintenance procedures:
1. The use of power handtools consisting of needleguns, sanders, flapper wheels, etc. are the most common methods of cleaning tiedowns. These handheld methods use mechanical abrasion to impact the area to be cleaned and remove unwanted coatings. These methods offer several disadvantages. Because they are handheld and bulky, the hard to reach underside areas of the tiedowns usually are not properly cleaned. The mechanical abrasion can impact surface contaminants such as chlorides, ferric oxide, and dirt into the abraded surface of the steel. These contaminants have been proven to cause premature failure of the coatings, especially in marine environments. The dust created by this mechanical abrasion also can be deposited on nearby clean steel causing contamination problems and recleaning costs. This method of cleaning is also slow and extremely labor intensive usually causing delays and coordination problems during the deck maintenance procedures. PA0 2. Abrasive blasting procedures consisting of both open blasting and contained devices is another method employed to clean tiedowns. These methods use an abrasive such as aluminum oxide, steel shot, etc. propelled at the surface by either mechanical or pneumatic means. The high velocity abrasives abrade the steel surface removing the existing paint. This abrasion can also cause trapped contaminants which can cause premature coatings failures. The abrasives can also escape containment and get into surrounding clean areas causing contamination problems. Because of the complex geometry of the tiedowns the abrasives can also rebound and become a hazard to anyone in the area. On abrasive equipment that is self-propelled the cleaning rates of the tiedowns are slower than the surrounding flat deck and the operator may have difficulty adjusting the speed of the device causing the tiedowns to be improperly cleaned. This then requires the recleaning of the tiedown usually with the mechanical methods discussed above. PA0 3. Open blasting using handheld ultra high pressure watedjets has been used to clean tiedowns in recent years on a limited basis. This generally consists of a handheld device that the operator places into the tiedown to remove the existing paint. This method eliminates many of the contaminant and abrasive problems but causes excessive amounts of water on the deck. This effluent water and paint debris has to be removed from the deck prior to recoating either the tiedowns or the surrounding deck. This delays the recoating process and possibly allows the formation of flashrust on the surfaces which also has to be removed prior to recoating. Automated self-propelled ultra high pressure watedjetting devices have been developed recently as noted below which use vacuum to contain the effluent water. These devices propel themselves on the deck surface and use a rotating bar or nozzle in a level plain parallel to the deck surface to clean the flat areas of the deck. These devices do not allow the manipulation of the nozzle into the tiedown and therefore do not clean the underside areas of the tiedowns. If the tiedowns are run over with these devices the paint and contaminants on the underside of the crossbars and the bottom of the cup areas are not removed and these areas have to be recleaned usually with the mechanical methods described above in 1. In addition to this problem, the seal that attaches the moving device to the deck usually losses its sealing properties as it crawls over the recessed or raised tiedowns and allows water to escape onto the clean deck. PA0 Some examples of this prior art are: U.S. Pat No. 4,809,383 3/1989 Urakami, Fukashi DEVICE CAPABLE OF SUCTION-ADHERING TO A SURFACE AND MOVING THEREALONG discloses a device that uses vacuum to attach a self crawling system to a flat surface. The device has a traveling function and a nozzle that is rotated about an axis that is perpendicular to the wall surface and travels parallel to the surface.